1. Field of the Invention
The present invention relates to a display apparatus, a manufacturing method of a display apparatus, and an electronic device, and more particularly, to a display apparatus, a manufacturing method of a display apparatus, and an electronic device each of which is configured not to give adverse influences of processing in the fabrication sequence to the electrode surfaces of pixels.
2. Description of the Related Art
An organic EL (Electro Luminescence) panel displays a video by supplying a current to respective pixels each having a vapor deposited organic electroluminescence layer or the like from the side or top or bottom of the panel by way of metal wires as is described, for example, in JP-A-2008-257086. When an organic EL panel becomes larger, necessary luminance of pixels increases and so does a current to be supplied. Also, because one wire becomes longer, wiring resistance becomes higher, which makes a voltage drop from the current supply end larger.
This voltage drop raises problems, such as the occurrence of non-uniform luminance and an increase of power consumption. Accordingly, a low resistance material is used for the current supply metal layer with the aim at suppressing a voltage drop. Examples of a low resistance metal include but not limited to aluminum (Al), copper (Cu), gold (Au), and silver (Ag). Of these candidates, Cu has a problem that it is quite difficult to form a wire from Cu whereas Au and Ag have a problem that they are expensive. In view of the foregoing, Al is often used as metal for low resistance wires.
Al can be processed by either wet etching or dry etching and is inexpensive. In a case where a single-layer Al wire is used, however, there is a concern about the generation of defects, such as hillock and spike.
The term, “hillock”, referred to herein means a semispherical protrusion generated on the wire surface due to heat history in the fabrication process. The term, “spike”, referred to herein means a phenomenon that Al enters into silicon (Si) when Al is subjected to heat treatment while in contact with Si.
As a countermeasure against these defects, there is a laminated structure to sandwich an Al wire between heat-resistant high melting point metal. As a consequence, a metal layer aimed at anti-hillock and anti-spike appears on the surface of the top metal layer when Al is used as a current supply metal layer.
A current flown through the current supply metal layer is injected into an organic electroluminescence layer by way of electrodes of pixels. It is therefore necessary for the electrodes of pixels to have a characteristic that they are capable of injecting a current into the organic electroluminescence layer. Normally, ITO (Indium Tin Oxide) having a high work function is used as a hole injecting electrode. As a consequence, metal with a high capability of injecting holes into the organic electroluminescence layer appears on the surface of a metal layer used as the electrodes of pixels.